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Testnet difficulty calculation changes, to take effect Feb 15 2012

Allow mining of min-difficulty blocks if 20 minutes have gone by without mining a regular-difficulty block.
Normal rules apply every 2016 blocks, though, so there may be a very-slow-to-confirm block at the difficulty-adjustment blocks.
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gavinandresen committed Dec 5, 2011
1 parent 4477b17 commit c52296a73e5222628bf6a03eaf727622594bf464
Showing with 29 additions and 4 deletions.
  1. +29 −4 src/main.cpp
@@ -768,6 +768,11 @@ static const int64 nInterval = nTargetTimespan / nTargetSpacing;
//
unsigned int ComputeMinWork(unsigned int nBase, int64 nTime)
{
// Testnet has min-difficulty blocks
// after nTargetSpacing*2 time between blocks:
if (fTestNet && nTime > nTargetSpacing*2)
return bnProofOfWorkLimit.GetCompact();

CBigNum bnResult;
bnResult.SetCompact(nBase);
while (nTime > 0 && bnResult < bnProofOfWorkLimit)
@@ -782,16 +787,36 @@ unsigned int ComputeMinWork(unsigned int nBase, int64 nTime)
return bnResult.GetCompact();
}

unsigned int static GetNextWorkRequired(const CBlockIndex* pindexLast)
unsigned int static GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlock *pblock)
{
unsigned int nProofOfWorkLimit = bnProofOfWorkLimit.GetCompact();

// Genesis block
if (pindexLast == NULL)
return bnProofOfWorkLimit.GetCompact();
return nProofOfWorkLimit;

// Only change once per interval
if ((pindexLast->nHeight+1) % nInterval != 0)
{
// Special rules for testnet after 15 Feb 2012:
if (fTestNet && pblock->nTime > 1329264000)
{
// If the new block's timestamp is more than 2* 10 minutes
// then allow mining of a min-difficulty block.
if (pblock->nTime - pindexLast->nTime > nTargetSpacing*2)
return nProofOfWorkLimit;
else
{
// Return the last non-special-min-difficulty-rules-block
const CBlockIndex* pindex = pindexLast;
while (pindex->pprev && pindex->nHeight % nInterval != 0 && pindex->nBits == nProofOfWorkLimit)
pindex = pindex->pprev;
return pindex->nBits;
}
}

return pindexLast->nBits;
}

// Go back by what we want to be 14 days worth of blocks
const CBlockIndex* pindexFirst = pindexLast;
@@ -1540,7 +1565,7 @@ bool CBlock::AcceptBlock()
int nHeight = pindexPrev->nHeight+1;

// Check proof of work
if (nBits != GetNextWorkRequired(pindexPrev))
if (nBits != GetNextWorkRequired(pindexPrev, this))
return DoS(100, error("AcceptBlock() : incorrect proof of work"));

// Check timestamp against prev
@@ -3120,7 +3145,7 @@ CBlock* CreateNewBlock(CReserveKey& reservekey)
pblock->hashPrevBlock = pindexPrev->GetBlockHash();
pblock->hashMerkleRoot = pblock->BuildMerkleTree();
pblock->nTime = max(pindexPrev->GetMedianTimePast()+1, GetAdjustedTime());
pblock->nBits = GetNextWorkRequired(pindexPrev);
pblock->nBits = GetNextWorkRequired(pindexPrev, pblock.get());
pblock->nNonce = 0;

return pblock.release();

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